Chemical Reaction Engineering

Asynchronous Video Series

Chapter 6, Part 1:

Series, Parallel and Complex Liquid Phase Reactions:

Selectivity, Mole Balances and

A-->B-->C in a Batch Reactor

H. Scott Fogler, Ph.D.

Multiple Reactions

Use molar flow rates and concentrations; DO NOT use conversion!

Types of Multiple Reactions

1. Series Reactions

2. Parallel Reactions

Multiple Reactions

Use molar flow rates and concentrations; DO NOT use conversion!

Types of Multiple Reactions

1. Series Reactions

2. Parallel Reactions

3. Complex Reactions: Series and Parallel

4. Independent

Selectivity and Yield

Instantaneous Overall

Selectivity

Selectivity and Yield

Instantaneous Overall

Selectivity

Yield:

Selectivity and Yield

Instantaneous Overall

Selectivity

Yield:

Example: (1) desired product , rD=k1CA2CB

(2) undesired product , rU=k2CACB

€

A + Bk

2 ⏐ → ⏐ ⏐ U1

Selectivity and Yield

Instantaneous Overall

Selectivity

Yield:

Example: (1) desired product , rD=k1CA2CB

(2) undesired product , rU=k2CACB

Run at high concentration of A. Therefore, use a PFR.

€

A + Bk

2 ⏐ → ⏐ ⏐ U1

Selectivity and Yield

(1) desired product , rD=k1CA2CB

(2) undesired product , rU=k2CACB

Add a third reaction.

(3)

€

A + Bk

2 ⏐ → ⏐ ⏐ U1

€

A + Bk

3 ⏐ → ⏐ ⏐ U2

€

rU 2= k 3C BC A

3

Selectivity and Yield

(1) desired product , rD=k1CA2CB

(2) undesired product , rU=k2CACB

Add a third reaction.

(3)

€

A + Bk

2 ⏐ → ⏐ ⏐ U1

€

A + Bk

3 ⏐ → ⏐ ⏐ U2

€

rU 2= k 3C BC A

3

€

SD/U1 /U 2=

k1CA2 CB

k 2CACB +k 3CBCA3then

€

=k1CA

k 2 +k 3CA2

CA

SD/U1/U2

Modification of the Algorithm for Multiple Reactions

Modification of the Algorithm for Multiple Reactions

Modification of the Algorithm for Multiple Reactions

Modification of the Algorithm for Multiple Reactions

Modification of the Algorithm for Multiple Reactions

Mole Balances

Mole Balances

Mole Balances

Mole Balances

Mole Balances

Net Rate of Reaction for Species A

Net Rate of Reaction for Species A

Series Reactions

Series Reactions

Series Reactions

, t=0 CA=CA0

Series Reactions

Series Reactions

Series Reactions

Series Reactions

Series Reactions

€

dCC

dt= k 2CB , t = 0 CC = 0